Liquid crystalline polymers (LCPs) are used in a variety of applications including molding resins. LCPs are used in a variety of applications because they have desirable (combination of) properties that other polymers have been unable to match. Many LCPs have good high temperature properties that are useful, for example from 250° C. to about 320° C. Some LCPs have claimed to be useful at higher temperatures but these have often had other drawbacks, such as poor processability, poor dimensional stability and/or poor thermal stability at their melt processing and/or use temperatures. Thus, LCPs with improved high temperature properties such as dimensional stability are of interest. Hence, it is desirable to have high temperature LCPs with good to excellent wear resistance at elevated PVs (pressure×velocity).
The following disclosures may be relevant to various aspects of the present invention and may be briefly summarized as follows:
U.S. Pat. No. 5,789,523 to George et al. discloses polyimide compositions that can be substantially improved by incorporating into the composition an inorganic, low hardness, thermally stable, sheet silicate, such as muscovite mica, talc and kaolinite, which results in improved wear resistance and reduced coefficient of friction. This patent discloses a blend material and does not disclose particulate polyimide.
U.S. Pat. No. 5,470,922 to Kaku et al. discloses polymeric blends of polyimide precursor resins and polyamides or polyesters, preferably in the form of liquid crystal polymers, provide polyimide products with excellent physical characteristics and injection molding capability. This patent does not disclose high temperature LCPs.
U.S. Pat. No. 5,312,866 to Tsutsumi et al. discloses a molding resin composition comprising 99.9 to 50% by weight of polyimide material and 0.1 to 50% by weight of PEK (polyether ketone) resin and/or polyester resin, and more particularly comprising the polyester resin capable of forming an anistropical molten phase at a temperature of 420° C. or less and a polyimide-based molding resin composition which comprises the said resins and other additives such as phenolic resin, fluororesin, graphite, carbon fibers, aromatic polyamide fibers, potassium titanate fibers and a crystallization accelerator, and is excellent in thermal resistance, chemical resistance, mechanical strength and processability.
U.S. Pat. No. 5,004,497 to Shibata et al. discloses a friction material containing 0.85 to 30 weight % carbon fibers and 2 to 20 weight % of aramid fibers. This friction material offers advantages in high temperature stability of the coefficient of friction, a favorable wear property, freedom from sticking and uneven wears, and superior anti-fade properties. This patent discloses a thermoset matrix material.